Influences of atmospheric circulation on the variability of wet sulfate deposition

✍ Scribed by Uri Dayan; Dennis Lamb

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 721 KB
• Volume: 28
• Category: Article
• ISSN: 0899-8418
• DOI: 10.1002/joc.1648

✦ Synopsis

Abstract

Precipitation chemistry data from the National Atmospheric Deposition Program were related to weather data from the Climate Diagnostics Center in order to reveal the influence of large‐scale circulation patterns on the wet deposition of sulfate downwind of the Ohio River Valley, where SO~2~ emissions were curtailed sharply in the mid‐1990s. The chemistry data from five precipitation‐sampling sites were combined to provide a regional average for each summer season over the 21‐year period from 1984 to 2004. The long‐term trend of sulfate concentration is associated to a statistically significant extent by composited flow patterns associated with the East Pacific–North Pacific index. The regional weather pattern for the sulfate‐rich years is associated with an intensification of the Bermuda High over the southeastern United States at the surface in tandem with a weakening of the 500‐hPa geopotential height (GPH) climatological trough located over the northeastern United States. The highest‐sulfate concentration days for the Atmospheric Integrated Research Monitoring Network (AIRMoN) Pennsylvania site occurred during a similar synoptic pattern when intense convection over the eastern United States was favoured thermodynamically. This study suggests that temporal changes in the large‐scale circulation pattern over North America need to be considered, in addition to changes in precursor emissions, as an explanation for the decreases in sulfate concentrations observed in summertime rains across the eastern United States. Copyright © 2007 Royal Meteorological Society